1. Field of the Invention
The present invention relates to systems and methods for crash energy management and, more specifically, relates to systems and methods for energy absorption in automotive applications utilizing a taper and flare energy absorption system.
2. Description of the Background
The design for crashworthiness is an extremely important aspect of vehicle and structural design. The primary aspect of crashworthiness design is providing a means to dissipate kinetic energy through the work of deformation within the vehicle structure. In the current energy absorption design systems, such as axially collapsed or inverted crush tubes, highly ductile material is critically important due to the severe strain states experienced during the deformation. Also, the amount of energy absorption is very sensitive to the quality and controls of the material. The available materials that meet these requirements, especially for non-ferrous metals, may be limited, and the resulting product cost may be significantly increased.
A typical prior art application may utilize an axial folding collapse technique, wherein a pre-dented hollow tube 100 is crushed lengthwise into a regular pattern 110 (see, FIG. 1). These triangular or other-shaped dents (not shown) force the crush tube to collapse into the xe2x80x9cnatural modexe2x80x9d which can then produce expected results. Typically, these prior art crush tubes 100 are made of aluminum alloys, but many other materials are also used. Some conventional crush tube assemblies may not contain any dents.
These conventional crush tubes are typically installed behind the front bumper section of an automobile or truck. The tube is affixed at one end to a rail on the chassis of the automobile and at the other end to the bumper. Hence, the force of a resulting collision that is perpendicular to the front face of the bumper will cause an axial compressive force on the installed crush tube, causing it to collapse. These tubes may also be installed in the rear bumper of automobiles or in any other orientation or system in which a spatially-confined absorption of an abrupt axial load is desired.
The conventional crush tube applications may suffer from one or more drawbacks that prevent their controlled use in many applications. For example, because of the intense crushing action, the tube must be made of a ductile metal, such as a special aluminum alloy. Such highly ductile metals are typically more expensive than less ductile materials. If materials with lower ductility are used, they may crack or split and therefore lose some or all of their energy absorption capacity.
Also, as seen in FIG. 1, the xe2x80x9ccrush zonexe2x80x9d 110 into which the tube 100 is compacted does not extend throughout the entire length of the crush tube 100. Hence, the uncrushed portions of the crush tube 100 are wasted in terms of energy absorption. Testing has shown that the conventional crush tube application may crush only approximately 70%-75% of the length of the crush tube.
Because of the intense and structured way in which the conventional application is crushed in a natural mode pattern, these crush tubes are typically made pursuant to very tight tolerances. Even small variations in the thickness of the material of the crush tube may cause a large variation in energy absorption during a crash event. For example, a weakness in one area of the tube may cause the tube to buckle in that area with a result that the tube does not perform as designed and may not absorb the requisite amount of energy for its intended application.
Even during normal operation, these conventional crush tube applications are not ideal. For example, the force dissipated by the xe2x80x9ccollapsingxe2x80x9d process oscillates around the mean force dissipation of the system. Therefore, high peaks of force are created by the conventional methods. These peak loads may cause a xe2x80x9cjerkingxe2x80x9d sensation to the passengers of the vehicle and may require that the backup structure be reinforced, thereby increasing the peak loads when crushing the backup structure. This may reduce passenger safety.
Also, because the existing technologies typically utilize only about 70% of the original crush tube length for energy absorption, high loads are needed to absorb the required energy in a given space. Therefore, in the case of automobiles, the accelerations imparted to the passengers are correspondingly high which may also adversely affect passenger safety.
These various limitations to the current implementation of axially loaded crush tube absorption systems are preferably addressed by one or more embodiments of the present invention.
In accordance with the present invention, there is provided an energy absorption system and method generally comprised of a crush tube, a taper component, and a flare component. The crush tube is inserted into a matching hole in the taper component. As the taper and flare components are moved over the crush tube, the taper component decreases the diameter of the crush tube and the flare component splits the crush tube into a plurality of petals. When mounted with the longitudinal axis of the crush tube parallel to an axis of an impact, the present invention is capable of absorbing some or all of the crash event by dissipating energy by the tapering, flaring, friction, and other methods.
The crush tube may include a plurality of initiator slits to aid in the flaring process, and the crush tube may have a circular, oval, square, rectangular, hexagonal, or other cross-sectional profile. The taper and flare components are preferably adapted to accept one or more of these crush tube orientations.
The present invention may utilize materials that are not acceptable for use with conventional axial crush absorption systems. For example, a material with less ductility may be used.
In at least one presently preferred embodiment, the invention is installed in a car, truck or other vehicle to partially or wholly absorb the shock of a crash event. For example, the energy absorption system may be mounted between a rail on the chassis or frame of the car and a bumper. Because the present absorption system generally dissipates energy along a single impact axis, two or more of the present absorption systems may be installed in a plurality of locations and orientations in a vehicle to absorb crash shocks from various impact angles and locations. The present invention may also be used in other axial load applications such as trains, barriers, elevators, carriers, and the like.
These and other features and advantages of the present invention will become readily apparent to persons skilled in the art from the following detailed description of the invention, the abstract, and the attached claims.